Orange-spotted grouper description

A rather large, robust marine fish, the orange-spotted grouper has an elongated body which is tan above, shading to whitish below. The head, body and median fins (the dorsal, anal and caudal fin) bear the numerous, small, orange or reddish-brown spots for which this species is named. The body also bears five faint, irregular dark bars, which divide into two towards the underside of the body. The tail is rounded, and the dorsal fin and anal fin bear small spines (3).

Related species

Orange-spotted grouper biology

The orange-spotted grouper feeds on fish, shrimps, crabs and cephalopods such as cuttlefish (2)(3). It is thought to use a relatively small home range(2) and is usually found alone or in small groups, although spawning aggregations of up to 5,000 have been reported (1). The main spawning period is between March and June in the Arabian Gulf (2)(4), and October to December in New Caledonia (1).

Like many groupers, the orange-spotted grouper has a fascinating life history, known as protogynous hermaphroditism. All orange-spotted groupers begin life as a female, reaching sexual maturity at around 2 to 3 years old, when 25 to 30 centimetres in length. When the female reaches around 55 to 75 centimetres, at approximately four years old, it changes sex and becomes a male (2)(3). The maximum age recorded for this species is 22 years (1).

Orange-spotted grouper range

The orange-spotted grouper occurs along continental shores and around large islands from the Red Sea to South Africa, eastward to the Western Pacific, where it is found from the Ryukyu Islands in Japan, south to Australia, and as far east as Palau and Fiji (1)(2)(3). It has also moved through the Suez Canal into the Mediterranean (1).

Species with a similar range

Orange-spotted grouper habitat

Adult orange-spotted groupers are generally found in estuaries, often in brackish water, and around protected, silty coral reefs. The species has also been found offshore to depths of 100 metres (1)(2)(3). Juveniles are common in estuaries and among mangroves (1).

Orange-spotted grouper status

Orange-spotted grouper threats

The orange-spotted grouper is widely targeted for food, for the live reef fish trade, and as a recreational fish. Although commonly produced in hatcheries, juveniles are also extensively taken from the wild for culture, particularly in Southeast Asia, so removing individuals that might otherwise go on to reproduce and supplement the wild stock (1)(2). This take is currently unregulated (1), and the fish farms can potentially bring their own problems, such as the spread of disease and parasites, water pollution, and the unsustainable capture of other fish species as feed (5). Habitat loss in the form of reef destruction and the loss of mangroves, a key nursery habitat for juveniles, is a further threat to the species (1).

For such a significant commercial fish, surprisingly little is known about the biology of the orange-spotted grouper, and there is a lack of accurate catch data, particularly as the species is often misidentified (1)(2)(3). However, populations are believed to be decreasing, with significant declines in catch rates reported in many areas (1)(2). It is unlikely that the heavy harvest of this species is sustainable in the long-term, particularly in light of its vulnerability to overexploitation as a result of its long lifespan, slow growth, and tendency to group together in spawning aggregations (1)(2)(4). In addition, the minimum sizes captured are often below the size of sexual maturity, and below the size at which sexual transition to the male occurs, so potentially leading to female-biased sex ratios and a lack of reproductive adults in the wild population (1)(4).

Orange-spotted grouper conservation

The orange-spotted grouper is completely protected in the waters of New South Wales, Australia, and minimum and maximum size limits for take are in place around Queensland (1)(2). The species also occurs in a number of Marine Protected Areas around Australia (2), including the Great Barrier Reef Marine Park, a World Heritage Area (6). In 2001, a number of tagged orange-spotted groupers were released on artificial reefs in Yan Chau Tong and Hoi Ha Wan Marine Park, Hong Kong, as part of a restocking trial (1).

Further conservation measures include regulations on fish farming. In Thailand, farms can only be set up in designated areas, and regulations are in place which aim to control environmental pollution and the spread of disease. The farms are run by local, small-scale fishermen, so benefitting local communities (5). Other suggested measures include further study into the orange-spotted grouper’s biology, taxonomy and catch rates, to more accurately assess its distribution and abundance (1)(2), as well as an increase in mesh size of traps and a reduction in fishing effort in some areas (4), and better protection of offshore areas where this impressive marine fish is thought to spawn(2).

Authentication

Glossary

In fish, an unpaired fin on the under surface of a fish, behind the anus.

Brackish

Slightly salty water, usually a mixture of salt and freshwater, such as that found in estuaries.

Caudal fin

The tail fin of a fish.

Cephalopod

From the Greek for ‘head-foot’, a class of molluscs that occur only in marine habitats. All species have grasping tentacles, and either an internal or external shell. Includes nautiloids, cuttlefish, squids, octopuses, and extinct ammonites and belemnites.

Dorsal fin

The unpaired fin found on the back of the body of fish, or the raised structure on the back of most cetaceans.

Home range

The area occupied by an animal during routine activities, which is not actively defended.

Protogynous hermaphroditism

A system in which an animal begins its life cycle as a female, but as it ages, based on internal or external triggers, it shifts sex to become a male animal.

Spawning

The production or depositing of large quantities of eggs in water.

Taxonomy

The science of classifying organisms, grouping together animals which share common features and are thought to have a common ancestor.

Carpenter, K.E. and Niem, V.H. (1999) The Living Marine Resources of the Western Central Pacific. Volume 4: Bony Fishes Part 2 (Mugilidae to Carangidae). Food and Agriculture Organisation of the United Nations, Rome. Available at: ftp://ftp.fao.org/docrep/fao/009/x2400e/x2400e36.pdf

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